This application is related to U.S. application Ser. No. 10/145,397 filed May 13, 2002, and U.S. application Ser. No. 10,145,398 filed May 13, 2002. The entire disclosures of these two other commonly filed U.S. applications are incorporated herein by reference.
This application is based on and claims the priority under 35 U.S.C. xc2xa7119 of German Patent Application 101 23 284.5, filed on May 12, 2001, the entire disclosure of which is incorporated herein by reference.
1. Field of the Invention
The invention relates to a pyrotechnic igniter arrangement with an integrated electronic assembly, especially for triggering passenger or occupant protection devices in motor vehicles, for example. The igniter arrangement includes a pyrotechnic charge or active mass operatively connected with an electrically ignitable ignition bridge.
2. Background Information
An igniter arrangement of the above mentioned general type is disclosed in German Patent Laying-Open Document DE 198 36 278 A1. According to that reference, the ignition bridge as well as an electronic assembly are arranged together on a carrier arrangement, whereby the entire carrier arrangement is arranged in the ignition capsule with the pyrotechnic charge or active mass. For protecting the carrier arrangement and the electronic assembly, the entire carrier arrangement is partially covered or coated with a shock absorbing, elastic material. The ignition bridge remains free of, i.e. is not covered by, the shock absorbing material, in order to enable the operative connection between the ignition bridge and the pyrotechnic charge.
German Patent DE 198 36 280 C1 discloses a pyrotechnic igniter arrangement, that is structurally separated by a protective wall into a pyrotechnic area or zone including the pyrotechnic charge and the ignition bridge, and an electronic area or zone including the electronic assembly. In order to connect the electronic assembly in the electronic zone with the ignition bridge in the pyrotechnic zone, separate contact elements are provided in the protective wall, whereby these separate contact elements must be contacted on both sides of the wall.
Further simpler carrier arrangements or substrates, for example circuit boards, to be used as a supporting carrier for the entire ignition arrangement including the ignition bridge and the electronic assembly, are disclosed in published European Patent Application 0,555,651 B1, for example. Using such a simple common carrier arrangement is more economical than providing separate carrier arrangements for the pyrotechnic zone and for the electronic zone respectively. However, such a simple carrier arrangement does not provide a comparably effective protection for the electronic assembly against the effects of pressure, temperature or forces that arise during the triggering or ignition of the igniter arrangement.
This can be disadvantageous, if the pressure, temperature, forces, or other mechanical influences arising from the pyrotechnic zone in turn are transmitted to the electronic assembly and lead to a disruption thereof. Namely, the igniter arrangement is typically connected via its electronic assembly to a databus, which in turn is further connected to a central unit and other igniter arrangements, for example in an ignition bus for occupant protection devices in a motor vehicle. It is desired that an igniter arrangement should remain at least partially functional even after its ignition, for example to confirm the proper ignition or the like. In any event, the electronic assembly must remain intact or undisturbed to an extent sufficient to assure that the further data exchange on the ignition bus will not be interrupted or interfered with by the igniter arrangement that has been ignited.
In view of the above, it is an object of the invention to provide an igniter arrangement which may be easily and economically manufactured, and which ensures that the electronic assembly still remains functional, even after triggering or ignition of the igniter arrangement. Particularly, it is an object of the invention to protect the electronic assembly in the electronic zone from the mechanical and thermal influences, and especially the mechanical forces, arising in the pyrotechnic zone of the igniter assembly during ignition thereof. The invention further aims to avoid or overcome the disadvantages of the prior art, and to achieve additional advantages, as apparent from the present specification.
The above objects have been achieved according to the invention in a pyrotechnic igniter arrangement with an integrated electronic assembly, comprising a carrier arrangement or substrate that extends into both a pyrotechnic zone and an electronic zone of the igniter arrangement, a pyrotechnic charge, an electrically ignitable ignition bridge arranged on a first portion of the carrier substrate in the pyrotechnic zone and operatively connected to the charge, an electronic assembly including at least one electronic component arranged on a second portion of the carrier arrangement in the electronic zone, a shock absorbing elastic first material that at least partially covers the first portion of the carrier arrangement in the pyrotechnic zone, whereby the ignition bridge itself preferably remains free of the shock absorbing first material, and a harder second material that at least partially surrounds or encases the second portion of the carrier arrangement in the electronic zone, whereby this harder second material is harder than the shock absorbing first material provided in the pyrotechnic zone.
The basic idea of the invention is to achieve the structural separation of the electronic zone and the pyrotechnic zone from each other, yet to simultaneously achieve the benefits of a simple common carrier arrangement for both the electronic assembly in the electronic zone as well as the ignition bridge in the pyrotechnic zone. Particularly, the invention provides a structural separation between the zones by encasing the carrier arrangement with respective materials having different hardnesses in the two zones, namely coating or covering the pyrotechnic zone with a shock absorbing, elastic, softer first material and encasing or completely potting the electronic zone with a relatively harder second material.
The inventive arrangement preferably comprises, within a housing, a complete encasing or potting of the pyrotechnic zone to the inner side walls of the housing with the shock absorbing first material, whereby however, the ignition bridge is of course excepted and is not completely encased in the shock absorbing material to allow its connection with the pyrotechnic charge. Similarly, the electronic zone is preferably fully encased or filled and potted out to the side walls of the housing with the relatively harder second material.
With the above described construction, although the electronic assembly is integrated into the ignition arrangement, and a single common carrier arrangement or substrate is provided for both the electronic assembly in the electronic zone and the ignition bridge in the pyrotechnic zone, a physical separation and decoupling of mechanical shock and thermal loads is achieved by the differential encasing of the two zones using two different materials. Namely, the carrier arrangement in the pyrotechnic zone is at least partially coated or encased with a shock absorbing elastic first material, while the carrier arrangement in the electronic zone is enclosed or encased with a second material that is harder than the shock absorbing first material of the pyrotechnic zone. This harder encasing of the electronic zone achieves a protection and a separation of the electronic assembly from the pyrotechnic zone, while the softer elastic encasing of the pyrotechnic zone additionally provides a shock absorbing effect that further diminishes the transmission of mechanical shock forces or other loads from the pyrotechnic zone into the electronic zone, and particularly into the electronic assembly. With such an arrangement, it is possible to omit an additional partition wall or separating protective wall between the electronic zone and the pyrotechnic zone.
The carrier arrangement further preferably comprises decoupling or parting features at a decoupling or parting location, for separating the pyrotechnic zone from the rest of the carrier arrangement, so that the excess forces that cannot be taken-up by the shock absorbing encasing at least will not be transmitted through the carrier arrangement to the electronic assembly.
In a preferred embodiment, the decoupling or parting features and/or the elastic encasing of the carrier arrangement in the pyrotechnic zone are so dimensioned, configured, and embodied, so that they will separate the carrier arrangement only when a thermal and/or mechanical load arising in the pyrotechnic zone or exerted on the carrier arrangement during the burning of the pyrotechnic charge exceeds a prescribed thermal and/or mechanical load threshold.